I always find it interesting to look at lists of the world’s largest companies from 60 years ago. For all of the monumental changes that have taken place over the last half century, the Fortune 500 from the year 1955 contains many names that are still familiar. Companies like Exxon, General Electric, and Proctor and Gamble remain among the world’s biggest corporations.

The biggest name at the time, though, was General Motors. From 1955 until the early 1990s, GM topped the Fortune 500 for most years in terms of both revenue and profit. Detroit was the equivalent of Silicon Valley during its heyday, and Americans obsessed over the biggest American car brands. At the time, the largest U.S. automakers basically controlled the market and generated enormous margins with little competition.

Eventually, other countries such as Japan became technically competent enough to build and export cars that were cheaper and more reliable, and the American firms saw their competitive advantage evaporate. GM last topped the Fortune 500 in 1992, and just seventeen years later the company filed for bankruptcy, saved from eternal oblivion only by the grace of the American taxpayer.

In the aftermath of that fiasco, analysts and commentators tried to explain what went wrong. Foreign competition, union greed, and inept management were all identified (by various sides) as the culprits. Perhaps all of them acted as catalysts in some way, but the bottom line for investors is that GM and other American automakers simply lost their pricing power.

In 2011, Apple took the title of world’s largest corporation, cementing Silicon Valley’s reputation as the new symbol of American technological prowess. Like GM in the 1960s, Apple has virtually no major competitors. While there are plenty of other smartphone brands on the domestic market, none can even hope to replicate Apple’s vast ecosystem of integrated products and services.

Among major U.S. corporations, Apple’s pricing power is virtually unparalleled. For what the iPhone costs to produce, Americans gladly pay a terrific premium. Although manufacturing of iPhone parts is mostly outsourced to places like southern China, almost all of the value added comes from the engineering and marketing expertise in Cupertino, which is why Apple (and not Foxconn) is the richest company on the planet.

Like GM, it seems likely that another competitor will someday dethrone Apple. Eventually other countries could develop the marketing and technical know-how to challenge Cupertino. As with automakers, a flood of imports could drive down producers down to marginal cost, which inevitably leads to someone going bankrupt.

Of course, that may not happen for many years. GM, after all, held onto its position for four decades before cars became just another commodity. Perhaps this logic is what led the famously tech-averse Warren Buffett to buy stock in Apple. But as Mad Eye Moody in the Harry Potter series always said, “constant vigilance” should be your mantra.